Constant Loop/Interest question

Write a C++ program that calculates a portfolio rise and fall over a number of market sessions. At each step of the way, you should display the new value of your hypothetical portfolio. During your bull markets, increase your portfolio by 20%. During your bear market, decrease your portfolio by 20%. In order to receive full credit, you must use a loop. IN ORDER TO RECEIVE FULL CREDIT, YOUR PROGRAM MUST DECLARE AND USE A const QUANTITY. The program dialogue should look exactly like this:

Enter a starting portfolio size:1000

After a bull market, your portfolio has grown to:1200.00

After a bear market, your portfolio has shrunk to:800.00

Continue(1=yes/0=no)? 1

Was it a bull or bear market (1=bull/0=bear)?1

Your portfolio is now 1200.00
After a bull market, your portfolio has grown to:1440.00

After a bear market, your portfolio has shrunk to:980.00

Continue(1=yes/0=no)? 1
Was it a bull or bear market (1=bull/0=bear)?0

Your portfolio is now 980.00
After a bull market, your portfolio has grown to:1176.00

After a bear market, your portfolio has shrunk to:784.00

Continue(1=yes/0=no)? 0
Was it a bull or bear market (1=bull/0=bear)?1

Your final portfolio is 1176.00

I have gathered that the const is going to be the interest of .2

How do I set up coding to show each scenario of interest added, or lost in a bull v. bear market and then prompt the user to continue and go through the method again??

Based on the example, once the user is done it would state "Your final portfolio...", in this case I would do an if statement to check if the user is done or not.
if(ans == 1)
{
//portfolio is
}
else
{
//final portfolio is
}